Laser fusion pulse shape controller

Abstract

An apparatus for controlling the pulse shape, i.e., the pulse duration and intensity pattern, of a pulsed laser system, and which is particularly well adapted for controlling the pellet ignition pulse in a laser-driven fusion reaction system. The apparatus comprises a laser generator for providing an optical control pulse of the shape desired, a pulsed laser triggered by the control pulse, and a plurality of optical Kerr-effect gates serially disposed at the output of the pulsed laser and selectively triggered by the control pulse to pass only a portion of the pulsed laser output generally corresponding in shape to the control pulse.

The invention claimed is: 
     
       1. An optical pulse shape controller comprising a first energy source responsive to an optical trigger signal to generate a light beam, a Kerr-effect gate including at least one Kerr cell disposed at the output of said first source and responsive to an optical control signal to gate only a selected portion of said light beam, said selected portion being a function of the duration and intensity pattern of said optical control signal, a second source of pulsed light energy, and means disposed at the output of said second source and responsive to an output light pulse from said second source to provide said optical trigger signal and said optical control signal of preselected duration and intensity pattern. 
     
     
       2. The controller set forth in claim 1 wherein said means disposed at the output of said second energy source comprises means forming an optical output pulse from said second source into a preselected pulse shape, means splitting said pulse of preselected shape into said optical trigger signal and said optical control signal, means feeding said trigger signal to said first source of electromagnetic energy and means feeding said control signal to said gate, said last-named means including means delaying said control signal to arrive at said gate at a time coincident with a selected portion of said beam. 
     
     
       3. The controller set forth in claim 2 wherein said Kerr-effect light gate comprises first and second optical Kerr cells serially disposed at the output of said first source, said control signal being fed to said first and second cells at times coincident with arrival thereat of said selected portions of said beam. 
     
     
       4. The controller set forth in claim 1 wherein both said preselected duration of said optical control signal and said duration of said selected portion of said light beam are in the picosecond range. 
     
     
       5. The controller set forth in claim 4 wherein said first energy source comprises a Q-switched laser, and wherein said second energy source comprises a mode-locked laser. 
     
     
       6. Apparatus for generating an electromagnetic energy pulse of preselected shape and duration comprising a first electromagnetic energy source responsive to a trigger pulse to provide a beam of electromagnetic energy, means including at least one Kerr-effect light gate disposed at the output of said first source and responsive to a control pulse to pass a selected portion of said beam, a second energy source providing a pulse of electromagnetic energy, and means disposed at the output of said second source and responsive to said pulse to provide said trigger pulse and said control pulse, said last-named means including means splitting said pulse into a plurality of separate pulses, means individually attenuating and delaying said plurality of split pulses, and means recombining said attenuated and delayed pulses into a composite pulse having a shape and duration corresponding to said preselected shape and duration. 
     
     
       7. The apparatus set forth in claim 6 wherein said pulse responsive means further includes means splitting said composite pulse into said trigger pulse and said control pulse, and means directing said control pulse onto said gate at a time coincident with the incidence on said gate of a selected portion of said beam.